The current iMac lineup will suit your needs if that's all you're really worried about. I know G4's running 10.4 or lower that can handle that easily and I've seen the aluminums do that and more easily. Make the switch if you really need it now and graphics aren't too much of a worry.
Well of course, I don't just want to run two applications at the same time. I want a solid, sturdy system that will last me a fair few years spec-wise. I also want it to have the power to play games. The Aluminum iMacs should be able to do that, right?